CN102803990B - Tracking method and measuring system having a laser tracker - Google Patents

Abstract

A target (9) equipped with a reflector (17) can be tracked in a measuring system comprising a laser tracker (10). The reflector (17) is tracked by means of a tracking unit (11) in a normal tracking mode and by means of a surveying device (13) in an extraordinary tracking mode. A capturing unit (12) having a detection range lying between the detection ranges of the tracking unit (11) and of the surveying device (13) is also present. If the target (9) cannot be detected by the tracking unit (11) but can be detected by the capturing unit (12), the orientation of the tracking unit (11) is controlled according to a measurement by the capturing unit (12). If the target (9) can then be detected by the tracking unit (11), a transition to the normal tracking mode is initiated.; If the target (9) can be detected only by the surveying device (13), the orientation of the tracking unit (11) is controlled according to a measurement of the surveying device (13).

Description

Tracking method and measurement system with laser tracker

technical field

The invention is in the field of measurement technology and relates to a tracking method and a measurement system with a laser tracker according to the preambles of the respective claims. The tracking method is used for the automatic tracking of a target point, in particular a moving target point, using the measurement beam of a laser tracker. The measurement system with laser tracker is equipped to carry out the method.

Background technique

The laser tracker mentioned several times is used for measuring the position of the moving target point. The term laser tracker is to be understood as a device having at least one distance meter which operates with a focused laser beam (referred to as measuring beam in the following description). For example, by means of a mirror rotatable about two axes, the direction of the measurement beam is aligned to the target point and the direction is detected with an angular position converter corresponding to the axis of rotation. The target point to be measured has a retroreflector (in particular a cube-corner prism or an arrangement of three mirrors arranged perpendicularly to one another), wherein the retroreflector guides the falling position of the laser tracker onto the retroreflector. Measurement rays are reflected back to the laser tracker. In this case, if the measuring beam falls exactly in the center of the reflector, the reflected measuring beam is distributed coaxially with the emitted measuring beam, and if the measuring beam does not fall in the center of the reflector, the reflected measuring beam There is a parallel displacement between the measuring beam and the emitted measuring beam. Depending on the embodiment of the tracker, an absolute distance between the laser tracker and the target point and/or a change in this distance can be drawn from a comparison of the emitted laser light and the reflected laser light. The position of the reflector or target point relative to the tracker is calculated from the angle acquired by the angle-to-position converter and the distance detected by the rangefinder.

A part of the reflected measuring beam is usually directed to a PSD (Position Sensitive Device). From the position at which the reflected measuring beam falls on the light-sensitive surface of the PSD, a parallel displacement of the reflected measuring beam relative to the emitted measuring beam is deduced. The measurement data thus determined define the parallel displacement of the reflected measuring beam and are used to control the direction of the measuring beam such that the measuring beam follows (tracks) the target point as it moves. That is to say, a corresponding change in the direction of the measurement beam or a corresponding change in the alignment of the mirrors aligned with the measurement beam ensures that the parallel displacement between the emitted measurement beam and the reflected measurement beam is reduced or kept as high as possible. very small.

It is clear that the control of the direction of the measuring ray by means of a parallel displacement between the emitted measuring ray and the reflected measuring ray has a small but non-negligible delay, which limits the movement of the target point and can be detected in the process. Tracking speed. If the target point moves faster, the measuring beam no longer falls on the reflector before its direction can be corrected accordingly, and thus both tracking and position measurement are interrupted. The same thing can happen if there is an obstacle between the tracker and the target point so that the measurement ray is interrupted. If the laser tracker or the measuring beam of the laser tracker "misses" the reflector, the operator is alerted to this and, if the tracker is equipped accordingly, a search routine can be started.

As soon as the target point is "found" again, that is to say the measuring ray falls on the reflector again and is reflected by it, the position of the target point can be measured and tracked again via the measuring ray, whereby The distance measurement must be restarted if necessary. The less controlled the movement of the target point and the smaller the reflectors used and the diameter of the measuring beam, the more frequent are the mentioned tracking interruptions. The same conditions as during the mentioned interruption of tracking usually also prevail at the beginning of the measurement process if the tracker is not aligned to the target point at all.

It is also known that laser trackers have a planar position indicator. This has as large a field of view as possible (e.g. larger than ) is arranged on the tracker and aligned such that the measurement beam can be directed to the target point identified on the camera image. The alignment of the measuring beam to the target point is initiated by an operator observing the camera image by correspondingly marking the image region in which the target point is imaged.

In WO2007/079601A1 a tracking method and a measuring system with a laser tracker are described, which have two tracking modes and when the measuring ray of the laser tracker "lost" the target point or "re-found" the target point , the measurement system switches from one tracking mode to another. The normal or formal tracking mode is the tracking known from laser trackers, which is based on the measuring beam, that is to say in this tracking, for example, a parallel displacement between the emitted measuring beam and the reflected measuring beam is detected and An attempt is made to reduce this displacement by changing the direction of the measuring beam. In normal tracking mode, the tracker detects the measurement ray reflected by the reflector and determination of the position of the target point is always possible. In a special tracking mode in which the measuring system operates when the tracker cannot detect the reflected measuring beam, the change in the direction of the measuring beam is controlled by means of the data recorded by the areal position indicator assigned to the laser tracker. The plane position indicator is, for example, a digital plane position camera providing image data, having a light-sensitive surface (eg CCD) and supplying the plane position camera with the usual for plane position indicators in all directions such as angle of view optics. However, the flat position indicator can also be, for example, a PSD (Position Sensitive Device) equipped with the same or similar optics, which only provides sensor-related position data, that is, direction data related to the device. From the data recorded by the plane position indicator, the direction towards the reflector is determined and an attempt is made to direct the measuring beam to the reflector by changing the measuring beam direction accordingly. The special tracking mode therefore works without detection of the reflected measuring beam, and precise determination of the position of the target point by means of the tracker is not possible in the special tracking mode. The special tracking mode is switched on as long as no reflected measuring radiation is detected in the tracker. In the special tracking mode, however, it is always checked again whether the reflected measuring beam is detected, and as soon as this is detected, the system switches again to the normal tracking mode and releases the position measurement.

Thus, the described apparatus and corresponding method make it possible to relocate "lost" target points and then relocate the target points again. But they are limited in their ability to follow rapid changes in the angular position of the target point relative to the tracker. This is especially important when the target point is near the tracker and the given absolute position changes—compared to a target point that is farther away—corresponding to the angle at which the target point is viewed from the tracker greater changes. Furthermore, the target point must remain relatively stationary for positioning until the acquisition can be terminated and the position measurement is activated again.

Similar tracking methods using cameras or sensors with narrow and wide viewing angles are also described in the following 3 publications:

EP 2 071 283 A2 describes the use of two separate cameras with wide and narrow viewing angles, each having its own light source coupled to the camera optics. The cameras are arranged separately from each other, one of which has a boresight that is in-line with the rangefinder and works with visible light. Object recognition is accomplished by switching on/off the corresponding light source and then forming the difference of the corresponding image, respectively.

WO 2009/046763 A1 shows two stages in object tracking, in which the optics are switched back and forth between a "short-range setting" with a wide viewing angle and a "long-range setting" with a narrow viewing angle.

US 7,292,788 B2 describes a laser-based communication using satellites in which "wide field of view" sensors and "narrow field of view" sensors are used to track received light rays. Figure 4B shows a device for two-stage measurements: To direct the laser rays into the fiber optics (640), an "intermediate/aquisition track" sensor (660) or a "fine track quad unit ( fine track quad cell)" (650). Other embodiments or experimental arrangements (FIG. 4A) also use a two-stage approach.

Contents of the invention

It is now the object of the present invention to provide a tracking method and a measuring system with a laser tracker for this tracking method, which allow the above-mentioned tracking interruptions to be overcome not only automatically but also with high dynamics. Another task is to provide the possibility to capture the target point again and start the position measurement again when the tracking is interrupted while the target point is moving. A further object is to provide a measuring system which allows a comparatively large aperture angle of the planar position camera.

The object is solved by a tracking method and a measuring system with a laser tracker as defined in the claims.

In the tracking method, a target equipped with reflectors is thus tracked by the measuring beam of the laser tracker. In the normal tracking mode, the measurement beam reflected by the reflector is detected in the tracking unit and the parameters for controlling the alignment of the measurement beam are calculated from this detection. In a special tracking mode in which no measuring ray reflected by the reflector is detected in the tracking unit, parameters for controlling the alignment of said measuring ray are calculated from data acquired by at least one other device. In this case, the laser tracker has a capture unit and a surface position indicator, wherein both the capture unit and the surface position indicator have a known position and orientation relative to the measuring beam. The acquisition unit has an acquisition area or an acquisition angle between the acquisition area of the tracking unit and the acquisition area of the planar position indicator.

The method performs the following steps in a special tracking mode:

■ If the target can be acquired by the capture unit, control the alignment of the measurement ray according to the angle at which the target is visible to the capture unit and check if the target is accessible to the tracking unit;

■ Then switch to normal tracking mode if the target can be acquired for the tracking unit;

■ If the target is only achievable for the PPI, control the alignment of the measurement ray according to the angle at which the target is visible for the PPI and check if the target is acquirable for the capture unit.

In other words, therefore, in the special tracking mode the parameters for controlling the alignment of the measuring beam are calculated from the data selectively acquired by the acquisition unit or by the planar position indicator and, if necessary, when positioning the target with the acquisition unit and Switch between locating the target with the planar position indicator until the target is acquired with the tracking unit. The steps described are therefore carried out repeatedly until transition to normal tracking mode.

As a result, the aperture angle or field of view of the planar position camera is no longer limited by the fact that the resolution of the planar position camera must be high enough to reliably capture objects by the tracker. An intermediately connected capture unit captures the target with the data of the surface position camera and refines the alignment of the tracker so that the target will be captured by the tracker.

The viewing angle or acquisition range of the surface position indicator can thus be increased so that the object can be followed even when the angle at which the measuring device sees the object changes rapidly, ie especially when the object moves in the vicinity of the measuring device.

If the target is detectable only for the surface position indicator, it is theoretically possible instead of aligning the measuring beam to initially also only align the capture unit. However, this generally also has the same meaning as the alignment of the measuring beam, since the capture unit and the tracking unit generally move relative to each other.

In a preferred embodiment of the invention, an absolute distance initialization for determining the absolute distance between the laser tracker and the target is performed (on the fly) when switching into normal tracking mode. Such methods are described, for example, in published patent applications EP 1647 838 A1 and US 2009/0033945. The distance to the target is thus also known based on the target's azimuth (relative to the laser tracker) and the altitude (Elevation).

In a further preferred embodiment of the invention, the level position indicator has a zoom function and thus an adjustable acquisition angle, and if the target cannot be acquired for the level position indicator at small acquisition angles, then a The following steps:

■ Increase the acquisition angle of the plane position indicator and check whether the target can be acquired for the plane position indicator;

■ If the target is available to the PPI, control the alignment of the measurement ray based on the angle at which the target is visible to the PPI; and

■ reduce the acquisition angle of the plane position indicator; or

■ Optionally, if the target cannot be acquired for the plane position indicator, then perform a search routine for locating the target by moving the plane position indicator.

In a further preferred embodiment of the invention, it is possible to selectively

■ In a first mode of operation of the deflection device, the tracking unit and the acquisition unit align or deflect their beam paths to the target,

■ Or in the second mode of operation of the deflection device, the flat position indicator

Align its optical path to the target or deflect it to the target. Here, the method has the following further steps:

■ If the tracking unit or the capturing unit acquires or searches for the target, it works in the first operating mode, or switches to the first operating mode;

■ If the level position indicator acquires or finds a target, then work in the second operating mode or switch to the second operating mode.

Therefore, in this preferred embodiment of the invention, the object is not simultaneously visible to the tracking unit and the surface position indicator, for example because the beam path of the tracking unit or the surface position indicator can be selectively switched by means of a tracking mirror. The light path is directed to the target. In this embodiment, if there is no capture unit, although it is possible to locate the moving target with the planar position indicator and to correct the alignment of the measuring beam accordingly, the alignment is no longer due to the time delay after the tracking mirror has been turned over. correct. In this case, the capture unit also allows the target to be captured in the event of an imprecise alignment after the mirror has been pivoted.

In a measuring system with a laser tracker, a target equipped with a reflector can be tracked by the measuring beam of the laser tracker. The laser tracker is equipped to detect with the tracking unit the measuring beam reflected by the reflector in normal tracking mode and to calculate parameters for controlling the alignment of the measuring beam from this detection, wherein the laser tracker is additionally equipped For, in a special tracking mode in which the measuring beam reflected by the reflector could not be detected in the tracking unit, to calculate parameters for controlling the alignment of the measuring beam from data acquired by at least one other device. In this case, the laser tracker has a capture unit and a surface position indicator, wherein both the capture unit and the surface position indicator have a known position and orientation relative to the measuring beam. The capture unit has an acquisition area located between the acquisition area of the tracking unit and the acquisition area of the planar position indicator. The laser tracker is equipped to carry out the above-mentioned method steps in a special tracking mode.

■ If the target can be acquired by the capture unit, control the alignment of the measurement ray according to the angle at which the target is visible to the capture unit and check if the target is accessible to the tracking unit;

■ Introduce a transition to normal tracking mode if it is possible for the tracking unit to acquire the target;

■ If the target is only achievable for the PPI, control the alignment of the measurement ray according to the angle at which the target is visible for the PPI and check if the target is acquirable for the capture unit.

In a preferred embodiment of the invention, the acquisition unit and the tracking unit use the same measuring radiation to determine the position of the reflector in their field of view. Alternatively, the acquisition unit can emit its own measurement light, which (outside the laser tracker) is distributed coaxially with the measurement beam of the tracking unit and passes through a common exit optics together with the measurement beam of the tracking unit.

In a further preferred embodiment of the invention, the beam path of the measuring beam—and the beam path of the measuring light of the capture unit, if this differs from the measuring beam—can be deflected onto the target by means of a deflection device. It is then possible to selectively

■ in the first mode of operation of the deflection device, the tracking unit and the capture unit align their beam paths to the target,

■ Alternatively, in the second mode of operation of the deflection device, the surface position indicator directs its beam path to the target.

In a further preferred embodiment of the invention, the acquisition unit emits measurement light which is parallel but not coaxial to the measurement beam of the tracking unit and passes through a separate exit optics. In this case, the capture unit preferably has its own light emitting means. Furthermore, both the capture unit and the tracking unit can operate with (ie be sensitive to) infrared light, wherein preferably the spectral sensitivity ranges of the capture unit and the tracking unit to incident light differ from each other and in particular do not overlap. Each of the two units therefore does not react to the light of the other unit.

In a further preferred embodiment of the invention, the capture unit has an image sensor for capturing images of the object. There is therefore not only a PSD which only provides the X and Y position signals of the light spot, but also a complete image with which, on the one hand, like the PSD, the measured values for tracking the target can be provided, but also other aspects of the laser tracker can be realized. Function. Such further functions are, for example, determining the orientation of objects, recognizing objects as objects, tracking objects by means of optical features (feature detection and object tracking). That is to say, non-point-like objects or entire light spot arrangements can also be detected and tracked.

Further preferred embodiments are given by the dependent claims. Features of the method claims can expediently be combined with features of the device claims and vice versa.

Description of drawings

The subject matter of the invention is explained in more detail below with the aid of a preferred exemplary embodiment shown in the drawing. Respectively schematically show:

Figures 1 to 3 are different embodiments of the present invention; and

4 and 5 are flowcharts corresponding to exemplary implementations of the method of the present invention.

The reference symbols used in the drawings and their meanings are summarized in the list of reference symbols. In principle, identical components are provided with the same reference symbols in the figures.

Detailed ways

FIG. 1 shows the structure of a laser tracker 10 in a first preferred embodiment of the invention. The laser tracker 10 comprises a tracking unit 11 with a measuring beam M, an acquisition unit 12 with an acquisition area E, and an areal position indicator 13 with an acquisition area L for positioning. The laser tracker 10 determines the azimuth and altitude and distance of the target 9 , preferably the retroreflector 17 on the target 9 , relative to the laser tracker 10 . An absolute distance meter (ADM) and/or an interferometric distance meter (IFM) are provided in the distance measuring unit 22 for determining and tracking the target distance. The plane position indicator 13 may have a zoom function.

The tracking unit 11 and the capture unit 12 use common exit optics 8, ie the light from and to both units is coupled onto a common optical path. This beam path contains the measuring beam and aligns a motorized tracking mirror 21 to a reflector 17 , for example a retroreflector such as a cube-corner prism or a triple mirror.

The tracking unit 11 has an image sensor or a PSD 14 (position sensitive device), which generates a signal corresponding to the position of the light spot on the area of the PSD. The tracking unit 11 works in a known manner by determining the position of the reflected measuring beam M on the PSD 14 in order to correct the alignment of the measuring beam M by means of the computing and control unit 19 and actuators for moving the tracking mirror 21 . The tracking unit 11 is therefore responsible for tracking the measuring beam with high precision and for this purpose comprises an acquisition region with collimated (parallel) measuring light whose measuring beam has a width of, for example, 1 mm to 2 mm.

Capture unit 12 has a camera or a two-dimensional image sensor 15 . The light rays generate light spots on the image sensor 15 . The light beam can be the reflected measuring beam (ie part of the light outcoupled from the measuring beam) or a second beam which is preferably distributed coaxially with the measuring beam M and which is coupled into the beam path of the measuring beam M but has a different wavelength. The capture unit 12 makes it possible to capture a moving object and to switch to object tracking by means of the tracking unit 11 even while the object is moving. The aperture angle acquired by the image sensor 15 is preferably approximately , so the total .

The plane position indicator 13 can be rotated at least about a vertical axis, optionally also about a height axis, together with the alignment of the measuring beam. The surface position indicator 13 optionally has an illumination device 16 , by means of which a reflective element (not shown) fastened to the object can be illuminated and thus can be illuminated for the surface position indicator 13 . nice to see. The lighting device 16 can also be configured to communicate with the target. The reflector 17 preferably has a light source 18 in order to be recognized by the flat position indicator 13 . The reflector 17 and the light emitting means 18 are arranged on the target 9 which may have a probe, for example. The luminous means 18 can also be used to determine the orientation of the target 9 by means of a surface position indicator or other cameras arranged on the laser tracker 10 , so that all six degrees of freedom of the target 9 can be determined. The surface position indicator 13 is preferably a light-sensitive camera in the visible range. The aperture angle acquired by the image sensor 15 is preferably approximately to . The plane position indicator 13 supplies the computing and control unit 19 with image data for analysis.

The data of the acquisition unit 12 and the tracking unit 11 are likewise processed by the computing and control unit 19 and used for tracking the reflector 17 when controlling the alignment of the measuring beam M. FIG. For this purpose, the computing and control unit 19 is designed, in particular programmed, to carry out the method according to the invention.

Therefore, the acquisition area or field of view or aperture angle of the capture unit 12 is larger than that of the tracking unit 11 , and the acquisition area of the planar position indicator 13 is larger than that of the capture unit 12 . Generally, the maximum aperture angle in the horizontal direction is approximately equal to the maximum aperture angle in the vertical direction. Then, the aperture angle is smaller or larger than the aperture angles of other cells in two directions respectively.

FIG. 2 shows the structure of a tracker 20 with an accessible planar position indicator 13 according to a second preferred embodiment of the invention. Here, only the features that differ from the first embodiment are described below: The areal position indicator 13 is here not aligned directly to the reflector 17 . Instead, the exit optics of the plane position indicator 13 are directed to the tracking mirror 21 . To operate the surface position indicator 13 , the tracking mirror 21 is turned so that the surface position indicator 13 always sees the reflector 17 through the tracking mirror 21 . A separate mechanical drive for aligning the surface position indicator 13 is thus not required. As a result, the surface position indicator 13 cannot be operated simultaneously with the tracking unit 11 or the capture unit 12 .

Fig. 3 shows the structure of a compact device 30 according to a third preferred embodiment of the present invention. Hereinafter only the features which differ from the first embodiment are described: the tracking unit 11 , the capture unit 12 and the surface position indicator 13 are arranged so as to move together on the carrier 31 . They are thus arranged in a fixed relationship to each other and are aligned together to the reflector 17 by a motor-driven movement of the carrier 31 relative to the base 32 . Capture unit 12 and tracking unit 11 here each have their own exit optics, but can also have a single, common exit optics. Along with the lighting means 16 for the surface position indicator 13 there is also a further lighting means 33 for the capture unit 12 . Preferably, said further light emitting means 33 emit light in the infrared range, and the capture unit 12 is only sensitive in the infrared range. The tracking unit 11 preferably has an image acquisition sensor in order to acquire deviations of the acquired measuring radiation from the setpoint position.

FIG. 4 shows a preferred variant of the sequence of the method of the invention. In normal tracking mode it is checked whether the measuring ray M of the laser tracker is reflected by the target 9 or the reflector 17 and is visible to the tracking unit 11 (first decision 202 "Locked?" concerning the detection of the reflected measuring ray ).

If yes, in a first tracking operation 203 “MEAS/ADJ” the position of the reflected measuring beam is determined in the tracking unit 11 (thus eg on the PSD 14 ), a corrective movement is calculated therefrom and the measuring beam M is tracked accordingly. Then continue with the steps of the first decision 202 .

If not, it is checked whether the target 9 is visible to the capture unit 12 . This is preferably also done with the aid of the measurement beam M, but with the aid of the position of the measurement beam M on the image sensor 15 (second decision 204 “captured?” concerning the detection of the object).

If yes, in a second tracking operation 205 “MEAS/ADJ”, the position of the reflected measuring beam is determined in the acquisition unit 12 , a corrective movement is calculated therefrom, and the measuring beam M is tracked accordingly. It is then checked in a third decision 206 “Positive locking?” concerning the detection of the reflected measuring beam whether the measuring beam M is visible to the tracking unit 11 .

■ If yes, then preferably update or re-execute the absolute distance measurement (Absolute Distance Initialization 207 "ADMinit"). Then continue with the steps of the first decision 202 .

■ If not, continue with the steps of the second decision 204 .

If the target 9 is not visible to the capture unit 12 , it is checked whether the target 9 is visible to the plane position indicator 13 (fourth decision 208 "OVC?" concerning the visibility of the target). This preferably takes place by means of reflection of light from the illumination means 16 on the target and/or by means of light emitting means 18 on the target 9 . Preferably, the luminous means and the surface position indicator 13 operate with light in the visible range.

■ If the target 9 is visible to the plane position indicator 13, the reflected measuring ray is determined in the plane position indicator 13 in the third tracking operation 209 "MEAS/ADJ", from which the corrective movement is calculated and correspondingly Track the measurement ray M. Then continue with the steps of the second decision 204 .

■ If the target 9 is not visible to the plane position indicator 13, for example the search routine 210 "SRCH" is executed. Such search routines are known per se. For example, changing the alignment of the tracker or at least the alignment of the optical axis of the plane position indicator 13 according to a predetermined template, and in the process constantly checking whether it is possible to align the plane position indicator 13 with the corresponding Object 9 is found on the corresponding image (fourth decision 208 ). If, for example, the search is still unsuccessful during a predetermined time or after the end of the entire routine, the system can be stopped, possibly with a corresponding notification to the operator.

When the measurement system is started 201 , it preferably starts with an object search using the maximum viewing angle, that is to say with a fourth decision 208 concerning the visibility of the object. In another preferred embodiment of the invention (not shown in the figure) the method is started by manually moving the target with the reflector 17 into the acquisition area of the tracking unit 11 and automatically by the tracking unit 11 and then tracked by the tracking unit 11. Then an absolute distance measurement is performed for the first time (similar to "ADMinit").

In a variant of the invention, if according to the first decision 202 no reflected measurement ray has been acquired in the tracking unit 11, the method is not continued with a second decision 204, but with a fourth decision concerning the visibility of the target. Decision 208 continues (dashed arrow in Figure 4).

FIG. 5 shows another modification of the flow of the method of the present invention in the case that the plane position indicator 13 has a zoom function: then the part framed by the dotted line in FIG. 4 can be replaced by the elements in FIG. 5 . The method then proceeds as follows:

If the object 9 is not visible to the plane position indicator 13 in the fourth decision 208 "OVC?", then at first the zoom objective 7 is adjusted to a larger viewing angle or acquired in the step 311 "zoom in" of the viewing angle opening angle, and in the fifth decision 312 "VIS?" concerning the visibility of the target it is checked whether the target 9 is visible to the plane position indicator 13 .

■ If the target 9 is not visible to the plane position indicator 13, for example the search routine 210 "SRCH" is executed, as described above.

■ If the target 9 is visible to the plane position indicator 13, in the fourth tracking operation 313 "MEAS/ADJ" the position of the reflected measuring ray is determined in the plane position indicator 13, from which the corrective movement is calculated, and The measurement ray M is traced accordingly. In the step 314 “Zoom out” of the angle of view reduction, the zoom objective 7 is set again to a smaller angle of view and continues with the steps of the fourth decision 208 .

In principle, other variants leading to the same result can of course also be used in the sequence of steps described.

In a preferred embodiment of the invention, the position of the luminous means 18 on the target 9 is known, and the plane position indicator 13 is already positioned on the plane position indicator 13 by means of this luminous means during capture, that is, also during the special tracking mode. The imaging at 13 determines at least one estimate of the orientation of the target 9 . Such methods for determining the orientation of the target 9 are known, but only associated with the normal tracking mode in which the distance between the tracker and the target is known precisely.

List of reference signs

7 Zoom optics 19 Calculation and control unit

8 common exit optics 20 tracker with accessible planar position indicator

9 goals

10 Laser tracker 21 Tracking mirror

11 Tracking unit 22 Absolute distance measuring device ADM and interferometer IFM

12 capture units

13 Flat position indicator for positioning 30 Compact device

31 carrier

14 PSD 32 Docks

15 image sensor 33 light emitting device for capture unit

16 Lighting device M Measuring beam

17 Reflector E capture area

18 Lights on target L Locating area

Claims (17)

1. A tracking method in which a target (9) equipped with a reflector (17) is tracked by a measuring ray (M) of a laser tracker (10), wherein in normal tracking mode, the tracking unit ( 11) detection of the measurement beam reflected by the reflector (17) and calculation of parameters for controlling the alignment of said measurement beam (M) on the basis of this detection, wherein also no detection in the tracking unit (11) in a special tracking mode of the measuring ray reflected by the reflector (17), calculating parameters for controlling the alignment of said measuring ray (M) from data acquired by at least one other device, It is characterized in that, The laser tracker (10) has a capture unit (12) and a planar position indicator (13), wherein both the capture unit (12) and the planar position indicator (13) have a known position relative to a measuring ray (M) and orientation, the capture unit (12) has an acquisition area located between the acquisition area of the tracking unit (11) and the acquisition area of the planar position indicator (13), and The method has the following steps in a special tracking mode: ■ if the target (9) can be acquired by the capture unit (12), the alignment of the measurement ray (M) is controlled (205) according to the angle at which the target (9) is visible to the capture unit (12), and Check if the target (9) can be acquired for the tracking unit (11); ■ Then switch to normal tracking mode if the target (9) can be acquired for the tracking unit (11); ■ If the target (9) can only be acquired for the plane position indicator (13), control (209) the measurement ray ( M) and check whether the target (9) can be acquired by the capture unit (12). 2. A method according to claim 1, wherein said steps are performed repeatedly until switching to normal tracking mode. 3. A method according to claim 1 or 2, wherein the following steps are carried out when switching into normal tracking mode: ■ Absolute distance initialization (207) for determining the absolute distance between the laser tracker (10) and the target (9) is performed. 4. The method according to claim 1 or 2, wherein the plane position indicator (13) has a zoom function and thus has an adjustable acquisition angle, and if at small acquisition angles for the plane position indicator (13) If the target (9) cannot be obtained, perform the following steps: ■ increasing (311) the acquisition angle of the plane position indicator (13) and checking whether the target (9) can be acquired for the plane position indicator (13); ■ If the target (9) is acquired for the plane position indicator (13), control (313) the measurement ray (M ) alignment; and ■ Decrease (314) capture angle of plane position indicator (13). 5. A method according to claim 4, wherein if the target (9) cannot be acquired for the plane position indicator (13), a search instance for locating the target (9) by moving the plane position indicator (13) is performed Cheng (210). 6. A method according to claim 1 or 2, wherein it is possible to selectively ■ In a first mode of operation of the deflection device ( 21 ), the tracking unit ( 11 ) and the capture unit ( 12 ) align their beam paths to the target ( 9 ), ■ or in the second mode of operation of the deflection device (21), the plane position indicator (13) aligns its beam path with the target (9), And said method has the following steps: ■ If the tracking unit (11) or the capturing unit (12) acquires, tracks or searches for the target (9), it works in the first operating mode, or switches to the first operating mode; ■ If the level position indicator (13) detects or finds the target (9), then work in the second operating mode or switch to the second operating mode. 7. A measuring system with a laser tracker (10), with which a target (9) equipped with a reflector (17) can be tracked by the measuring beam (M) of the laser tracker (10), wherein the laser tracks The reflector (10) is equipped to, in normal tracking mode, detect with the tracking unit (11) the measuring beam reflected by the reflector (17) and calculate from this detection the alignment for controlling said measuring beam (M) Parameters, wherein additionally the laser tracker (10) is equipped for, in a special tracking mode in which the measurement ray reflected by the reflector (17) cannot be detected in the tracking unit (11), according to at least one other data acquired by the device to calculate the parameters used to control the alignment of the measurement ray (M), It is characterized in that, The laser tracker (10) has a capture unit (12) and a planar position indicator (13), wherein both the capture unit (12) and the planar position indicator (13) have a known position relative to a measuring ray (M) and orientation, the capture unit (12) has an acquisition area located between the acquisition area of the tracking unit (11) and the acquisition area of the planar position indicator (13), and The laser tracker (10) is equipped for, in special tracking mode: ■ if the target (9) can be acquired by the capture unit (12), the alignment of the measurement ray (M) is controlled (205) according to the angle at which the target (9) is visible to the capture unit (12), and Check if the target (9) can be acquired for the tracking unit (11); ■ Introduce a switch to normal tracking mode if the target (9) can be acquired for the tracking unit (11); ■ If the target (9) can only be acquired for the level position indicator (13), control the measurement ray (M) depending on the angle at which the target (9) is visible for the level position indicator (13) Align and check if the target (9) can be acquired for the capture unit (12). 8. The measurement system with laser tracker (10) according to claim 7, wherein the capture unit (12) uses the same measurement ray (M) as the tracking unit (11) to determine the reflector (17) in its field of view s position. 9. The measurement system with laser tracker (10) according to claim 7, wherein the capture unit (12) emits measurement light coaxially with the measurement ray (M) of the tracking unit (11) and with the measurement The rays pass together through a common exit optics ( 8 ). 10. The measuring system with laser tracker (10) according to claim 8 or 9, wherein the beam path of the measuring beam can be deflected onto the target (9) by means of a deflection device (21), and if the measuring beam of the capture unit (12) Unlike the measuring ray, the optical path of the measuring light can be deflected onto the target (9) by the deflection device (21). 11. The measuring system with laser tracker (10) according to claim 10, wherein it is possible to selectively ■ In a first mode of operation of the deflection device ( 21 ), the tracking unit ( 11 ) and the capture unit ( 12 ) align their beam paths to the target ( 9 ), ■ Alternatively, in the second mode of operation of the deflection device ( 21 ), the surface position indicator ( 13 ) aligns its beam path with the target ( 9 ). 12. The measurement system with laser tracker (10) according to claim 7, wherein the capture unit (12) emits measurement light which is parallel to but not coaxial with the measurement ray (M) of the tracking unit (11) and passes through through a separate exit optics. 13. The measuring system with laser tracker (10) according to claim 12, wherein the capture unit (12) has its own light emitting means (33). 14. The measurement system with laser tracker (10) according to claim 13, wherein both the capture unit (12) and the tracking unit (11) work with infrared light, and the capture unit (12) and the tracking unit (11) Spectral sensitivity ranges for incident light differ from each other. 15. The measurement system with laser tracker (10) according to claim 14, wherein the spectral sensitivity ranges of the capture unit (12) and the tracking unit (11) for incident light do not overlap each other. 16. Measuring system with laser tracker (10) according to one of claims 7 to 9, wherein the surface position indicator (13) has zoom optics (7). 17. Measuring system with laser tracker (10) according to one of claims 7 to 9, wherein the capture unit (12) has functions for acquiring images of the target (9) and for determining measured values for tracking the target ( 9) Image sensor.